1. Field of the Invention
It is desirable in various lubricating formulations to obtain materials which are stable in the lubricant and which impart antioxidant properties to the lubricating composition. The present invention deals with beta-dithioalkanol reaction products and aromatic amines or hindered phenols which are suitable in lubricating compositions.
2. Description of the Art
It is known from an article entitled The Condensation of 2-Hydroxyethylsulfides with Alcohols and Phenols by Richter et al, Journal of Polymer Science, Volume XLI, Pages 4076-4079, that a beta-dithiodialkanol when reacted in the presence of hydrochloric acid and an alcohol will give the corresponding ether as a reaction product. The technology in the Richter article is further reported in U.S. Pat. No. 2,582,605 issued Jan. 15, 1952.
It is suggested in German published patent application No. 1,520,040A that Guerbet alcohols may be condensed with thiodialkylols at a molar ratio of 1:0.5-0.9. U.S. Pat. No. 4,366,307 issued Dec. 28, 1982 to Singh et al describes non-crystallizing, water, solvent, fuel and temperature resistant liquid polythioethers having 2-4 terminating radicals and at least 8 repeating sulfur-containing units.
Further information with regard to the polymerization of a beta-thiodialkanol is found in Thioglycol Polymers I Hydrochloric Acid-Catalyzed Auto Condensation of Thiodiglycol by Woodward, Journal of Polymer Science, Volume XLI, Pages 219-223 (1959). The hydroxyl groups in the beta position relative to the sulfur in an aliphatic chain are stated to be of unusual reactivity in the Woodward article. Further information on such beta-dialkanols is found in Thioglycol Polymers III Copolymerization of Thiodiglycol and Similar Thioglycols with Aliphatic Hydroxy Compounds by Andrews et al, Journal of Polymer Science, Volume XLI, Pages 231-239 (1959). The Andrews' reference describes copolymers obtained from dihydroxy compounds where one of the compounds is thiodiglycol. Aromatic sulfur-containing compounds containing beta-hydroxy groups and their reaction properties are discussed in an article entitled Nucleophilic Substitution of Hydroxyl Groups in 2-Alkyl (Aryl)-Thioethanols by Fokin et al., Bull. Acad. Sci. U.S.S.R. Div. Chem. Sci. 1982, Pages 1667-1672 (1982).
U.S. Pat. No. 2,943,112 to Popoff et al issued June 28, 1960, describes the preparation of diphenylamine compounds. Popoff et al also states that the diphenylamine compounds are useful as anti-oxidants in rubber compositions.
It has, however, now been discovered that products having exceptional anti-oxidant properties may be obtained through mixtures of an aromatic amine such as an alkylated diphenylamine and the reaction product of a monohydric alcohol and a beta-thiodialkanol. The subject compositions are particularly suited for automobile automatic transmission fluids.
Throughout the specification and claims, percentages and ratios are by weight, temperatures are in degrees Celsius and pressures are in KPa gauge unless otherwise indicated. To the extent that any of the references cited in this application are relevant to the present invention, they are herein incorporated by reference.